Manually actuated positioning control system



United States Patent 4 Claims. (Cl. 60-52) This invention relates to the art of positioning controls and more particularly to a steering system.

It is among the objects of the invention to provide a positioning control system designed to elfect alternate positioning of a movable member, which system may be manually actuated and which has relatively few parts which are not likely to become deranged and which when the steering wheel is not actuated will automatically cut off flow to and from the actuator effecting the steering action without changing the set position of the actuator controlled by the steering wheel.

According to the invention, these objects are accomplished by the arrangement and combination of elements hereinafter described and more particularly recited in the claims.

In the accompanying drawings the single figure illustrates one embodiment of the invention.

Referring now to the drawings, the system comprises a pump unit 11 of conventional type such as a bi-directional volumetric metering pump, put out by the Ross Gear & Tool Company of Lafayette, Ind. The pump unit 11 is controlled by a steering wheel 12 so that depending upon the direction of rotation of the steering wheel, fluid under pressure will be provided at the ports 13 or 14 respectively of said pump.

The ports 13 and 14 are connected respectively by lines 15 and 16 through one-way valves 17 and 18 to junction 19, the one-way valves being positioned so that they will permit flow only from the junction 19 to the respective ports 13 or 14 as the case may be.

The pump 11 is designed to control a hydraulic control valve 21 which in turn controls the flow of fluid under pressure to an actuator 20.

The distributor valve 21 comprises a cylindrical casing 22 having a bore 23 therethrough, the ends of which are closed by end plugs 24, 25.

The casing 22 has a discharge port 26 located substantially centrally of the length thereof, said discharge port 26 being in communication with an internal annular groove 27 in the bore of said casing. A reservoir 28 is connected by line 29 to a fluid inlet port 31 also in communication with said annular groove 27. The casing 22 also has two pairs of ports 33, 34 and 33', 34' positioned respectively on opposite sides of the annular groove 27, the ports 33, 33 defining control outlet ports and the ports 34, 34 defining control inlet ports. The bore of the casing 22 has a plurality of annular grooves 35, 36 and 35', 36 aligned respectively and in communication with the ports 33, 34 and 33, 34'.

Slidably mounted in the casing 22 of distributor valve 21 is a valve member or spool 41 which is normally retained in the neutral position shown. To this end, the casing 22 is formed from two parts, i.e., parts 22a and 2212. One end of part 22a is of reduced external diameter and is externally threaded to receive the correspondingly threaded end of part 22b as at 42 and said part 22b is of reduced diameter adjacent its free end as at 43 defining an annular shoulder 44.

Positioned in the casing part 22b and seated against annular shoulder 44 and the annular shoulder 45 defined by the reduced diameter end of part 22a, are washers 46 and 47, each of which has a central opening 46' and 47 therein. The washers are normally retained against the associated shoulders 44 and 45 by an intervening coil spring 49, the portion of said part 22b between the washers defining a pressure chamber 51. In addition to the chamber 51, a second chamber 65 is provided between the end plug 25 and the adjacent end 66 of the valve member 41.

The valve member 41 has a central annular groove 52 defining two spaced end portions 53, 54. As is shown in the drawing, the end portions 53, 54 each has an annular groove 55 at each end thereof defining a sealing rim 56,

57 therebetween, the sealing rims ,56, 57 being of outer diameter just slightly less than the inner diameter of bore 23 of the casing 22 to define a high precision sliding seal. The depth of each of the annular grooves 55 is extremely small so that said grooves define capillary passageways. The length of each of the end portions 53, 54 is such that with the valve member 41 in the neutral position shown, the inner edges a, a of each of the end portions 53, 54 respectively, will extend inwardly beyond the associated annular grooves 35, 35 and the outer ends b, b of each of said end portions 53, 54 will extend outwardly beyond the associated annular grooves 36, 36', the inner ends a, at extending beyond the associated annular grooves 35, 35' by an amount greater than the outer ends b, b' extend beyond their associated annular grooves 36, 36'.

It is to be noted that the capillary grooves 55 are of such small size that when the valve member 41 is in neutral position shown, there will be substantially no flow through the ports 33, 34 and 33', 34'.

The portion of the valve member 41 adjacent the end 12 thereof has an axially extending stem 61, defining an annular shoulder 62 adapted to abut against the washer 47. The stem 61 is of diameter considerably smaller than that of the openings 46, 47 in the washers and extends through both of said washers with ample clearance, a nut 63 being screwed on the free end of said stem on the outer side of said washer 46 to act as an abutment in the manner hereinafter to be described.

Each of said chambers 51, 65 has a port 51', 65 leading thereinto, said ports being connected respectively by lines 68, 69 to the ports 14 and 13 of the pump 11.

The hydraulic actuator 20 comprises a cylindrical casing 71 having a piston 72 slidable therein. A piston rod 73 connected to said piston extends axially through both ends 74, 75 of said actuator 20 and is designed to actuate the device to be operated. The actuator 22 has two ports 76, 77 located respectively on opposed sides of the piston and connected respectively by lines 78 and 79 to junctions 81, 82. Each of the junctions 81, 82 is connected by lines 83, 84 to the associated control outlet port 33, 33' and by lines 85, 86 through one-way valves 87, 88 to the control inlet ports 34. 34' respectively, the valves 87, 88 permitting flow only in direction from said control inlet ports.

In the operation of the system shown in FIG. 1, when steering wheel 12 is rotated it will create a differential between the pressure at ports 13 and 14 and, for example, a greater pressure at port 13 than at port 14. As a result of the lower pressure at port 14, fluid from reservoir 28 will flow through line 29 into annular groove 52 and then from discharge port 26 to junction 19 and through oneway valve 18 and line 16 into port 14 to furnish a constant supply of oil to the system. At the same time, due to the higher pressure developed at port 13, there will be a flow of fluid under presusre through line 69 into port 65 of the distributor valve and into pressure chamber 65 thereof to react against the end 66 of the valve member 41.

- Due to the capillary passageway 55, there will be high pressure in such passageway, but no flow and the same 3 high pressure with no flow will appear in the capillary pasageway 55 on the left side of the sealing rim 57 due to the one-way valve 88 and lines 86, 84. As a result, since the pressure on both sides of the sealing rim 57 will be the same, the end portion 54 will not be laterally displaced and hence free movement of the valve member is permitted, since friction is minimized.

When the pressure in chamber 65 rises sufiiciently to overcome the force exerted by coil spring 49, the valve member 41 will then move to the left. As soon as the end b of the valve member moves slightly past annular groove 36', there will be a slight cracking of the annular groove 36' so that flow will be permitted therethrough. It is to be noted that since the end a of the end portion 53 extends inwardly beyond annular groove 35 an amount more than the end b of end portion 54 extends outwardly beyond annular groove 36, the annular groove 36' will crack before the annular groove 35 will crack. Since the gas contained in the actuator 20 is generally about of the volume thereof when the latter is in neutral position there will be a slight flow of fluid through port 34', one-way valve 88, line 79 into port 77 of the actuator to compress the gas therein but there will be no flow of fluid from port 76 of the actuator at this time since port 33 is still closed.

With further rotation of the steering wheel 12, there wlil be corresponding greater buildup of pressure in chamber 65 and hence further movement to the left of the valve member 41 sufiicient to cause the annular groove 35 to crack slightly. As a result, the fluid in the actuator on the left side of the piston 72 thereof will then be forced through port 76, lines 78 and 83 into annular groove 35 and thence into annular groove 52 through discharge outlet 26 to junction 19, through one-way valve 18 and line 16 back to the port 14 of the pump 11.

By reason of the one-way valve 88, for example, when the annular groove 36 is open and the piston 72 is moving to the left, if the member controlled by the piston rod 73 should strike an obstruction so that there is a momentary stoppage of movement, no back flow or reaction can occur since the valve 88 will close. As a result, there will be no transmittal of the road reaction to the steering wheel since any back flow will be restrained by the one-way valve 88. This is particularly desirable when the tractor, for example, being steered is very heavy and slow moving. Where the tractor is light and is capable of higher speeds then road reaction would be desirable and the one-way valves 88, 87 could be removed.

It is to be noted that when the pump is turned in the reverse direction there will be a pressure buildup in chamber 51 and due to the relatively large opening 47 in washer 47, fluid will flow through said opening to react against the associated end of the valve member 41. The operation, when the steering wheel is turned in the reverse direction, is identical to that previously described, except that fluid under pressure will then flow into the port 76 of the actuator 22.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A position control system comprising a reversible hydraulic actuator having a pair of control ports, a source of fluid under pressure comprising a reversible 4 pump having two fluid ports, a distributor valve interposed between said control ports of said actuator and said source of fluid under pressure, said distributor valve comprising a casing having a bore therethrough, a valve member slidably mounted in said bore, said valve member comprising a substantially cylindrical spool having a substantially central annular groove defining two end portions, each end portion having a reduced diameter annular portion at each of its ends defining a central rib therebetween, each of said reduced diameter portions defining a capillary passage, said distributor casing having two pairs of longitudinally positioned control ports, said reduced diameter portions on each end portion of said spool being aligned with the respective pairs of control ports when the valve member is in neutral position to close said ports, means normally retaining said valve member in neutral position to cut oil flow of fluid into and out of the control ports of said valve member, said casing having a pair of control chambers operatively connected respectively to the fluid ports of said pump and in communication with opposed ends of said valve member to eifect movement of the latter when the pressure in one of said chambers exceeds a predetermined amount, means connecting the control ports of each pair to an associated actuator control port, means connecting the pair of capillary passages on each of the end portions of said spool, whereby when pressure is applied from said source of fluid to said chambers, the capillary passages, when in alignment with the control ports, will prevent flow of fluid through said control ports, but provide equal pressure on both sides of the associated rib thereby to balance the ends of the spool to minimize friction between the ribs and the bore of the casing, said valve member being conformed to connect said source of fluid under pressure applied to one of said chambers to one of said control ports of said actuator when the pressure in such chamber exceeds a first predetermined amount to eifect a corresponding movement of said valve member, while restraining flow of fluid under pressure from the other control port of said actuator until the pressure in such chamber has exceeded a second predetermined amount to effect further movement of said valve member.

2. The combination set forth in claim 1 in which a one-way check valve is connected between the outermost control port of each pair of control ports of the distributor valve and the associated control port of the actuator to permit flow only from the distributor valve control port to the actuator control port.

3. The combination set forth in claim 1 in which a line connects the two fluid ports of said pump, a pair of one-way check valves positioned in said line, said casing having a pair of additional ports between said control ports, said additional ports being aligned with said central groove in said spool, a reservoir connected to one of said additional ports, said other additional port of said distributor valve being connected to said line between said valves, said valves permitting flow only in direction from said other additional port to the fluid ports of said pump.

4. The combination set forth in claim 1 in which resilient means are provided normally retaining said valve member in neutral position.

References Cited UNITED STATES PATENTS 2,020,951 11/1935 Lemon 6052 2,722,102 11/ 1955 Pilch 60-52 2,984,985 5/1961 MacMillin 6097 EDGAR W. GEOGHEGAN, Primary Examiner. 

1. A POSITION CONTROL SYSTEM COMPRISING A REVERSIBLE HYDRUALIC ACTUATOR HAVING A PAIR OF CONTROL PORTS, A SOURCE OF FLUID UNDER PRESSURE COMPRISING A REVERSIBLE PUMP HAVING TWO FLUID PORTS, A DISTRIBUTOR VALVE INTERPOSED BETWEEN SAID CONTROL PORTS OF SAID ACUATOR AND SAID SOURCE OF FLUID UNDER PRESSURE, SAID DISTRIBUTOR VALVE COMPRISING A CASING HAVING A BORE THERETHROUGH, A VALVE MEMBER SLIDABLY MOUNTED IN SAID BORE, SAID VALVE MEMBER COMPRISING A SUSBTANTIALLY CYLINDRICAL SPOOL HAVING A SUBSTANTIALLY CENTRAL ANNULAR GROOVE DEFINING TWO END PORTIONS, EACH END PORTION HAVING A REDUCED DIAMETER ANNULAR PORTION AT EACH OF ITS ENDS DEFINING A CENTRAL RIB THEREBETWEEN, EACH OF SAID REDUCED DIAMETER PORTIONS DEFINING A CAPILLARY PASSAGE, SAID DISTRIBUTOR CASING HAVING TWO PAIRS OF LONGITUDINALLY POSITIONED CONTROL PORTS, SAID REDUCED DIAMETER PORTIONS ON EACH END PORTION OF SAID SPOOL BEING ALIGNED WITH THE RESPECTIVE PAIRS OF CONTROL PORTS WHEN THE VALVE MEMBER IS IN NEUTRAL POSITION TO CLOSE SAID PORTS, MEANS NORMALLY RETAINING SAID VALVE MEMBER IN NEUTRAL POSITION TO CUT OFF FLOW OF FLUID INTO AND OUT OF THE CONTROL PORTS OF SAID VALVE MEMBER, SAID CASING HAVING A PAIR OF CONTROL CHAMBERS OPERATIVELY CONNECTED RESPECTIVELY TO THE FLUID PORTS OF SAID PUMP AND IN COMMUNICATION WITH OPPOSED ENDS OF SAID VALVE MEMBER TO EFFECT MOVEMENT OF THE LATTER WHEN THE PRESSURE IN ONE OF SAID CHAMBERS EXCEEDS A PREDETERMINED AMOUNT, MEANS CON- 